The present invention relates to a multi-pile type delivery apparatus for a sheet-fed printing press, which alternately deliveries printed and conveyed paper sheets to a plurality of sheet stacking units lined up in a sheet convey direction.
Generally, in a sheet-fed printing press, a paper sheet printed by a printing press is transferred from the grippers of a printing cylinder to the delivery grippers of delivery chains, and conveyed as the delivery chains travel. When the delivery grippers holding the paper sheet abuts against the sheet release cam at the convey end portion, the paper sheet is released from the delivery grippers, falls and is stacked on the pile of the delivery apparatus. Conventionally, a multi-pile type delivery apparatus is proposed in which a plurality of sheet stacking units, i.e., piles are lined up in the sheet convey direction. For this reason, when the number of paper sheets stacked on the pile reaches a predetermined number, the printing press need not be stopped to change the pile. In this case, a sheet release cam is provided above each sheet stacking unit. A cam switching means is provided in correspondence with each sheet release cam except for the most downstream cam to individually move the sheet release cam between a sheet release position where the sheet release cam abuts against the delivery grippers to cause the paper sheet to be released and a retreat position where the sheet release cam retreats not to abut against the delivery grippers. An adjusting unit for moving and adjusting the position of the sheet release cam is provided to each sheet release cam. The adjusting unit selects an optimum sheet release position and an optimal sheet release timing in accordance with the printing speed, the sheet size, the sheet thickness, or the sheet material, thereby preventing sheet misalignment or sheet jamming in the delivery unit.
Sheet-fed printing presses having such a cam switching means or movement adjusting units for a sheet release cam are disclosed in Japanese Utility Model Laid-Open Nos. 63-161253 and 4-5452, and Japanese Patent Laid-Open No. 58-167348. However, the movement adjusting unit of the sheet release cam disclosed in Japanese Utility Model Laid-Open No. 63-161253 has a structure in which the swinging fulcrum of the sheet release cam is free to shift inside an elongated hole, one end of a lever swingably supported at the central portion is pivotally mounted on the sheet release cam, and the other end is coupled to a piston rod. When the piston rod is moved, the swinging fulcrum of the sheet release cam is shifted inside the elongated hole, and at the same time, the sheet release cam is pivoted about the swinging fulcrum. For this reason, the sheet release cam is nonlinearly moved to make it difficult to correctly adjust the position, and when a cam follower abuts against the cam, the lever directly applies a load on the piston rod. The cam switching means disclosed in Japanese Utility Model Laid-Open No. 4-5452 has a structure in which the cam is vertically escaped with respect to the traveling direction of the cam follower. For this reason, when the printing speed is increased, it becomes difficult to set the timing of cam switching. In the worst case, the cam strikes the cam follower from the side to damage the printing press. The cam switching means disclosed in Japanese Patent Laid-Open No. 58-167348 has a structure in which one end and the other end of the lever swingably supported are simply coupled with the piston rod and the sheet release cam, respectively. For this reason, when the cam follower abuts against the cam, the lever directly applies the load on the piston rod.